Open Forum
New Delhi, 17 April 2024
Heat Wave Conditions
FATAL IMPACT ON HUMAN HEALTH
By Dhurjati Mukherjee
The past
year, 2023 was the hottest year on record with mean temperature nearing the
critical 1.50 Celsius threshold over a 12-month period and the trend
continued in the first two months of this year. For India, 2023 was the second
warmest year on record in the country since 1901. Projections reveal the
current year may surpass this record as apart from April, the next two months
may become unbearable in western, northern and eastern parts of India.
Moreover, the coastal cities with high humidity as also the desert regions may
give a feeling of anything around 42 to 45 degrees Celsius.
Given
the forecast,Prime Minister Modi called a meeting last week to take stock of
the preparedness for heatwave conditions and advised that governments at
central, state and district levels must work in synergy.
The annual
‘State of Climate Report’of World Meteorological Organisation(WMO), says
the global mean temperature in 2023 was 1.450C -- 0.2 degree Celsius
above 1850-1900 average, turning it the warmest year in 174-year history of
record keeping. Besides, it broke records in all climate indicators, including greenhouse
gas levels, ocean heat, sea level rise, Antarctica sea ice loss and glacier
retreat.
It’s distressing
touching the critical 1.50Celsius threshold so early has negated projection
of Paris Agreement, hailed globally. “Never have we been so close to the 1.50
C limit of the Paris Agreement on climate change”, observed WMO Secretary General
Celeste Saulo, sounding the red alert to the world. Thus, the question now
would be whether warming would reach 2 or 2.50 C in the next two
decades.
India
observed a significant mean temperature increase of 0.15 degrees C per decade
since 1950, according to a 2020 Ministry of Earth Sciencesassessment. The
observed warming is not occurring evenly across India. Warm days and warm nights
have also increased at about seven and three days per decade, respectively,
during 1951-2015 and even later. Currently, 23 States, mainly of plain and
coastal regions, are considered more vulnerable to widespread heat impact.
However, that doesn’t mean hilly states are safe. Although their maximum
temperatures do not reach heatwave threshold levels of 45 degrees C, the
population is experiencing higher temperatures compared to previous
decades.
The
warming has been in focus for quite some time. A UN report about two years
back, says India would become the worst climate-affected region in the world,
specially applicable to the cities. Even this report could not contemplate that
global warming of 1.5 degrees centigrade would be reached by 2023.
At same
time, the report predicted various trends which include: Rise in weather and
climate extremes led to some irreversible impacts as natural and human systems
are pushed beyond their ability to adapt; Approximately 3.3 to 3.6 billion
people live under climate threat; Beyond 2040, climate change will lead to
numerous risks and multiple climate hazard will occur simultaneously; Coastal
cities are under severe climate risk which includes Mumbai, Chennai, Kolkata,
Bhubaneswar etc.
Human
health exposure to severe or continuous heat, leads to heat stress. When
uncompensated, heat stress manifests as heat-related illnesses. Such illnesses
range from superficial/mild and manageable (e.g. prickly heat, heat-related
swelling, heat cramps, heat exhaustion) to a medical emergency (i.e. heat
stroke). Heat stroke is the most severe of heat-related illnesses as it impairs
brain function (i.e. stroke) due to uncontrolled body heating. It may turn into
a critical condition that often turns fatal if there is a delay or failure in
reducing body temperature by rapid, active cooling. Besides neurological
impairment, high core body temperature (at least 40 degrees C), or hot, dry
skin are other heat stroke symptoms.
Heat-related
illnesses are not the only cause of emergency or mortality during hot summer
days. Normal human body temperature stays within a narrow range of 36.3-37.3
degrees C. It maintains thermal balance through radiation (40%), evaporation
(30%), convection (27%), and conduction (3%). Any external or internal
condition that increases body temperature invokes various physiological
responses changing cardiovascular, kidney, and metabolic systems, driven by
increased blood flow to the skin and dehydration. Various studies have
indicated that 90% of India is found to be vulnerable to heatwave impact.
Epidemiologically,
it is important to note; in current scenario, whichever threshold is used to
announce heatwaves, the health impacts of heat do not begin to occur only after
those threshold temperature levels are crossed. Health impacts begin much
before, even at moderate temperature levels. In terms of external factors,
humidity plays a crucial role in creating heat stress by limiting our body’s
major cooling mechanism: sweating.
Even at
moderate temperatures, like 35 or 36 degrees C, if the relative humidity is
70%, it will feel like 50 degrees C to us. In terms of internal factors, heat’s
impacts depend on the acclimatisation and build-up of heat stress in the human
body. Acclimatisation is a gradual physiological adaptation (short-term) that
increases heat tolerance as a person incrementally exerts in a hot setting for
a few days. Air conditioning and comorbidities reduce our heat tolerance.
Similarly, long-term adaptation occurs in people living in hotter regions over
the years. Therefore, tourists from colder regions are particularly at risk of
heat stroke.
The Union
Health Ministry cautioned amid weather forecasts of excess days of heat waves
across the country during Lok Sabha elections. The National Programme on
Climate Change and Human Health (NPCCHH) advisory on extreme heat underlined
that physical exertion, direct sun exposure and difficult access to shade and
water may worsen the health of vulnerable people. Infants, and young children
and people with cardiovascular diseases or high blood pressure are among the
vulnerable populations. Not just stroke but heat related illnesses include heat
rash, heat oedema (swelling of hands, feet and ankles) and fainting.
A study
conducted in Kolkata for2021-22 summer found that indoor heat index levels
in urban slum dwellings were 5.29 degrees C higher than outdoors. Dangerously
high heat and humidity (at least 45 degrees C) remained for an average of about
nine hours/day in urban slum dwellings compared to 2 hours a day in rural
houses. These differences were particularly notable at night. During the
coolest time of night, the insides of urban dwellings recorded a 6.4 degrees C
higher heat index than outdoors, while the insides of rural houses recorded 1.3
degrees C above outdoor levels. Cement walls, clay tiles, corrugated tin roofs,
fewer rooms, and crowding made urban slums dangerously hot.
Similarly,
a study from Ahmedabad recorded an average 6.7 degrees C higher heat index
at the locations where patients with acute heat illnesses were picked up by
emergency medical services compared to what was recorded by the nearest weather
station during the summer of 2016. At city level, such differences translate
into an increase in all-cause mortality with daily city temperature. Hence,
city-level temperature-mortality study has become vital for heat-health action
planning.
Adaptation
measures to extreme heat are essential as the situation has the potential to
change the course of irreversible planetary consequences. Due to rise in
greenhouse gases, global warming has reached alarming levels. Even with all the
commitments made by different nations and the very recent aim of targeting net
zero emissions, large numbers of people in tropical countries, including India,
will find it hard to live. Thus, a health-centric adaptation focus should be
seriously followed in every sector to tackle the ongoing heat wave. This will
also help us stay on course for achievement of the SDGs.---INFA
(Copyright, India News & Feature Alliance)
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